Control valve

ABSTRACT

A control valve for use in a split braking system having an indicating member movable from a normal position to a translated position in the event of the failure of one of the separately supplied fluid pressures acting thereon. A proportioning member is biased toward the indicating member and movable in response to a predetermined value of the other supplied fluid pressure toward metering engagement with the indicating member in its normal position to thereafter effect a metered applied fluid pressure in a predetermined ratio with the other supplied fluid pressure. The proportioning member is provided with a pair of opposed areas respectively subjected to the other supplied and applied fluid pressures to effect the predetermined ratio, and a third area is also provided on said proportioning member for subjection to the other supplied fluid pressure and additive to one of the opposed areas to alter the predetermined value of the other supplied fluid pressure at which the proportioning member is actuated to effect metering engagement with the indicating member in its translated position.

United States Patent [1 1 Stokes CONTROL VALVE Inventor: Stanley L.Stokes, Florissant, Mo.

Assignee: Wagner Electric Corporation,

Newark, NJ.

Filed: Sept. 8, 1971 Appl. No.: 178,715

Related US. Application Data Division of Ser. No. 8,480, Feb. 4, 1970,Pat. No. 3,627,385.

[56] References Cited UNITED STATES PATENTS 3,441,318 4/1969 Bueler303/6 C Primary Examiner-Duane A. Reger Assistant Examiner-E. R.Kazenske Attorney-Joseph E. Papin -A6 J 2g 28 -21 17 27 3 A1 22/27O A[451 June 12,1973

[57] ABSTRACT A control valve for use in a split braking system havingan indicating member movable from a normal position to a translatedposition in the event of the failure of one of the separately suppliedfluid pressures acting thereon. A proportioning member is biased towardthe indicating member and movable in response to a predetermined valueof the other supplied fluid pressure toward metering engagement with theindicating member in its normal position to thereafter effect a meteredapplied fluid pressure in a predetermined ratio with the other suppliedfluid pressure. The proportioning member is provided with a pair ofopposed areas respectively subjected to the other supplied and appliedfluid pressures to effect the predetermined ratio, and a third area isalso provided on said proportioning member for subjection to the othersupplied fluid pressure and additive to one of the opposed areas toalter the predetermined value of the other supplied fluid pressure atwhich the proportioning member is actuated to effect metering engagementwith the indicating member in its translated position.

14 Claims, 3 Drawing Figures 37 16 35o 2T 0 0 280 22a 1: Q -5 1 6oCONTROL VALVE This is a division of application Ser. No. 8,480, filedFeb. 4, 1970 now U.S. Pat. No. 3,27,385 issued Dec. 14, 1971.

SUMMARY This invention relates generally to control valves and inparticular to those utilized in horizontally split brake systems. 7

The control valve in accordance with the present invention is especiallydesigned for use in a horizontally split braking system. In such a brakesystem, it may be readily realized by those skilled in the art to whichthis invention relates that the magnitude of the fluid pressure at whichmetering or proportioning to the rear brakes is indicated should beappreciably greater in the event of the failure of one of the splitsystems. This is, of course, due to the fact that the entiredeceleration of the vehicle is dependent on only one-half of the brakingcapability or potential of the vehicle when one of the horizontallysplit systems has failed.

The present control valve provides an indicating member which is movablefrom a normal position toward opposed translated positions in saidcontrol valve to indicate the failure of one of the separate fluidpressures of the split braking system supplied thereto, and a pair ofproportioning members are provided for metering engagement with saidindicating member to effect separate metered applied fluid pressuresthrough said control valve in a predetermined ratio with the separatefluid pressures supplied thereto. The proportioning members are actuatedin response to a predetermined value of the supplied and applied fluidpressures into metering engagement with the indicating member in itsnormal position, and said proportioning members include means foreffecting actuation thereof into metering engagement with saidindicating member in response to another predeterminedv value of thesupplied and applied fluid pressures. having a magnitude greater thanthe first named predetermined value when said indicating member is inone of its translated positions.

RELATED PATENTS This patent application is related to U.S. Pat. No.3,441,318 issued to Richard C. Bueler on Apr. 29, 1969, and assigned tothe common assignee of this patent application and is a patentablydistinct improvement thereof.

DRAWING DESCRIPTION FIG. 1 is a sectional view showing a control valveem bodying the present invention in cross-section,

FIG. 2 is an enlarged fragmentary view showing the rightwardproportioning piston of the control valve of FIG. 1 in cross-section,and

FIG. 3 is a graphical representation of the input and output fluidpressures of the control valve of FIG. 1.

Referring nowto the drawings in detail and in particular to FIG. 1, acontrol valve 1 for use in a horizontally split braking system (notshown) is provided with a housing 2 having a bore 3 therein interposedbetween opposed stepped counterbores 4, and 4a, 5a, and opposedshoulders 6, 6a and 7, 7a are respectively defined between said bore andsaid counterbores4, 4a and between said counterbores 4, 4a and 5, 5a. Across-bore 8 is also provided in the housing 2 having one endintersecting the bore 3 adjacent the mid-portion thereof while the otherend thereof connects with a threaded cross-bore 9 which is provided toreceive an electrical switch indicated generally at 10, to be discussedhereinafter. Inlet ports 11, 11a, which are respectively connected withthe separate fluid pressure generating chambers of a split mastercylinder (not shown), are provided in the housing 2 intersecting thecounterbores 5, 5a, and outlet ports 12, 12, which are connected toright and left rear brakes, are respectively provided in the housing 2intersecting with the counterbores 4, 4a adjacent to the shoulders 6,6a. Closure members or end plugs 13, 13a are threadedly received in theopen ends of the housing counterbores 5, 5a, and stepped bores l4, 15,16 and 14a, 15a, 16a are provided in said closure members, respectively.Annular shoulders or abutments 17, 18 and 17a, 18a are provided on theclosure members 13, 13a between the stepped bores 14, 15 and l5, l6 andbetween the stepped bores 14a, 15a and 15a, 16a respectively. Annularspacers or seal seating members 19, 19a are positioned in the steppedbores 14, 14a in engagement with the shoulders 17, 17a and provide aseat or abutment for annular sealing members 20, 20a which are sealablyengaged with the stepped bores 14, 14a, and annular sealing members 21,21a are seated on the shoulders 18, 18a in sealing engagement with thestepped bores 15, 15a.

An indicator or switch actuating member, indicated generally at 22, isprovided with opposed abutting pistons 23, 23a slidable in the housingbore 3 and having opposed enlarged head portions 24, 24a slidable in thehousing counterbores 4, 40. Peripheral seals 25, 25a are carried in thepistons 23, 23a in sealing engagement with the housing bore 3, andperipheral seals 26, 26a are carried in the piston head portions 24, 24ain sealing engagement with the housing counterbores 4, 4a between theinlet and outlet ports 11, 11a and 12, 12a. Mating or substantiallycoaxial lands or positioning portions 27, 27a are provided on thepistons 23, 23a being normally positioned beneath the housing crossbore8, as shown, and peripheral locking grooves 28, 28a are provided in saidpistons between said land portions and the seals 25, 25a. Referring nowalso to FIG. 2, stepped bores 29, 30 and 29a, 30a are provided in thepiston heads 24, 24a, and the larger of said stepped bores 29, 29aintersects with the opposed end portions 31, 31a of said piston headswhile the smaller of said stepped bores 30, 30a are intersected by acrosspassage 32, 32a provided in the pistons 23, 23a.

Metering or proportioning members, such as the pistons indicatedgenerally at 33, 33a, are provided with head portions 34, 34a integrallyformed with and interposed between stop members 35, 35a and reducedstepped extensions 36, 36a and 37, 37a. The heads 34, 34a are providedwith a plurality of radially extending, hexagonally shaped guides 38,38a, and proportioning or metering springs 39, 390 are precompressedbetween said heads and retainers 40, 40a to respectively urge saidretainers and the piston stops 35, 35a into abutment with the interiorends of the closure members 13, 13a and the switch pistons 23, 23a.Annular peripheral grooves 41, 41a are provided in the piston heads 34,34a having annular base walls 42, 42a interposed between radiallyextending defining valve members for engagement with annular sealing orseating members 45, 45a. The sealing members 45, 45a are provided withannular base portions 46, 46a defining proportioning aperturestherethrough and interposed between opposed sides 47, 47a and 48, 48a.The seal sides 48, 48a are normally seated in abutting engagement withthe opposed ends 31, 31a of the switch pistons 23, 23a and define valveseats for engagement with the valve members or groove side walls 44,44a. The seals 45, 450 are also provided with annular peripheral lips49, 49a in sealing engagement with the housing counterbores 4, 4a, and aplurality of return flow passages 50, 50a are provided between the sealsides 48, 48a and the lips 49, 49a, said return flow passages normallybeing closed by the sealing engagement of said lips with said housingcounterbores, respectively.

Inlet chambers 51, 51a are defined in the housing counterbores 4, 5 and4a, 50 between the closure members 13, 13a and the sealing members 45,45a, and said inlet chambers are in open pressure fluid communicationwith the inlet ports 11, 11a at all times. Other or changeover chambers52, 520 are defined in the closure member stepped bores 15, 150 betweenthe seals 20, 21 and 20a, 21a, and said change-over chambers are adaptedfor selective subjection to atmospheric fluid pressure and the fluidpressure at the inlet ports 11, 11a, as discussed hereinafter. Outletchambers 53, 53a are defined in the housing bore 3 and counterbores 4,4a substantially between the sealing members 45, 45a and the seals 25,25a being connected in open pressure fluid communication with the outletports 12, 12a at all times. The switch pistons 23, 23a are provided withopposed cross-sectional areas A,, A defined by the sealing engagement ofthe seals 25, 25a with the housing bore 3 and also opposedcross-sectional seals 26, 26a with the housing counterbores 4, 4a. Theannular seating engagement of the sealing member sides 48, 48a with theswitch piston ends 31, 31a define opposed effective areas A .4 which aresubjected to the fluid pressures at the inlet ports 11, 11a acting onthe sealing members 45, 45a. The proportioning piston heads 34, 34a areprovided with cross-sectional areas A A substantially defined by thesealing engagement of the valve members 44, 440 with the sealing members45, 45a which are respectively subjected to the fluid pressures at theoutlet ports 12, 12a. The sealing engagement of the closure member seals20, 20a and 21, and 21a with the proportioning piston stepped extensions36, 36a and 37, 37a define cross-sectional areas 14 ,14 and A A on theproportioning pistons 33, 33a. The areas 14 ,14 and 11 ,14 arerespectively subjected to the atmosphere and the fluid pressures in thechangeover chambers 52,52a, and the areas 11 A, and A A, are additiveand opposed to the areas A,,A,,,, respectively. It should be noted thatthe areas A A, are predeterminately greater than the areas ri /1 and theareas 14 ,14 are greater than the areas A ,A respectively.

The electrical switch includes a conductive closure or plug member 60threadedly and conductively received in the open end of the housingcrosscounterbore 9, and a metal terminal 61 extends through said plugmember and is insulated therefrom, said terminal having anexterior endfor connection in an electrical circuit of a type well known to the artforselectively energizing a driver warning or dash lamp (not shown). Anon-conductive switch follower member 62 is slidably received in a bore63 provided in the plug member 60 and has a lower end portion extendingthrough the housing cross-bore 8 into positioning engagement with theswitch piston lands 27, 27a. To complete the description of the controlvalve 1, a conductive contact 64 is provided adjacent to the upper endof the follower member 62 for electrical engagement with another contact65 on the plug member 60, and a current carrying spring 66 is interposedbetween the interior end of the terminal 61 and the follower membercontact 64 urging the lower end of said follower member into followingor positioning engagement with the switch piston lands 27, 27a andurging the follower contact 64 toward engagement with the plug membercontact 65.

In the operation with the component parts of the control valve 1positioned as shown in the drawings, separately supplied or input fluidpressures P normally having substantially equal magnitudes are suppliedupon actuation of a tandem or split system master cylinder (not shown)to the inlet ports 11, 110, respectively, of said control valve. Theinput fluid pressures P,,P flow from the inlet ports 11, 11a into theinlet chambers 51,51a acting on the opposed areas A A, of the switchpistons 23, 23a to establish substantially equal and opposed forcesP,A,,P A, and the input fluid pressures P,,P flow from said inletchambers through the sealing member apertures 46, 46a and the switchpiston stepped bores 29, 30 and 29a, 30a and cross-passages 32,32a intothe outlet chambers 53, 53a to establish output or applied fluidpressures P,,,,P at the outlet ports 12,12a having magnitudessubstantially equal to those of the input fluid pressures P ,P Since theforces P A P A are substantiallY equal and opposite, the switch pistons23,23a are normally maintained in their centered positions, as shown.

The output fluid pressures P P act on the effective areas ri /1 of theproportioning pistons 33,33a proportioning pistons against thecompressive forces F,Fa of the metering springs 39,39a; however, themetering spring forces F,Fa prevent movement of said proportioningpistons until the input fluid pressures P P and the output fluidpressures P P exceed a predetermined value, as shown by the point R onthe line OT in the graphical representation of F 10. 3. When thepredetermined value R of the input fluid pressures P P and output fluidpressures P is attained, the closing forces P,,A .,,P ,,A overcomes themetering spring forces F,Fa to move the proportioning pistons 33,330from their original positions in directions outwardly of the switchpistons 23,23a toward isolating positions. The movement of theproportioning pistons 33,33a to their isolating positions engages thevalve members 44,440 with the sealing member valve seats 48,48a closingthe sealing member apertures 46,46a to isolate the input fluid pressuresP P, in the inlet chambers 51,51a from the output fluid pressures P P inthe outlet chambers 53,53a, and upon the engagement of said valvemembers with said valve seats, the input fluid pressures P i, act oneffective input areas A -A ,A ,,A,,, to establish input forces P,(A,-AP,(A ,,A which are additive to the spring forces F ,Fa to substantiallybalance the opposed output forces P,,,A,,P,,,A established by the outputfluid pressures P P acting on the effective output areas 11 A, of saidproportioning pistons. With the proportioning pistons 33,33a in theirisolating positions, the opposing forces P A P A acting on the switchpistons 23,23a are eliminated and replaced by the substantially equaland opposing forces P,A,,P A which are established by the input fluidpressures P P acting on the areas A A of the sealing members 45, 45a inseating engagement with the switch piston ends 31,3111.

- From the graphical representation in FIG. 3, it is obvious thatincreases in the magnitudes of the input fluid pressures P P in excessof the predetermined value R, as shown by the line ORT, will result inproportionally reduced increases in the output fluid pressures P P asshown by the line RS. For instance, when the input fluid pressures P,,Pare increased to a value in excess of the predetermined value R, theinput forces P (A- -A P (A -A are correspondingly increased and additiveto the metering spring forces F ,Fa to overcome the output forces P ,,A,P ,,A therefore, the metering pistons 33, 33a are moved in an inwarddirection toward the switch pistons 23,23a to metering positionsdisengaging the valve members 44, 44a thereof from the sealing membervalve seats 48,48a to effect metered applications of the increased inputfluid pressures P P through the sealing member apertures 46,46a and theoutlet chambers 53,53a to the outlet ports 12,12a to effect proportionalincreases of the output fluid pressures P P in a predetermined ratiowith the input fluid pressures P P at the inlet ports 11, 11a, as shownby the line RS in the graph of P =[P (A -A FHA, and P =[P (A A Fa]/A Ofcourse, the increased output fluid pressures P P effect a correspondingincrease in the output forces P ,,A P A and when the increased outputforces P, A,,,P ,,A attain an increased value substantially equal tothat of the increased input forces P (A -A P w -A and the additivemetering spring forces F,Fa, the proportioning pistons 33,33a are againmoved outwardly toward their isolating positions to re-engage the valvemembers 44,44a with the sealing member valve seats 48,48a to againisolate the increased input fluid pressures P and the increased outputfluid pressures P P It is, of course, obvious that the proportioningpistons 33,33a will be responsive to further increases in the inputfluid pressures P P to effect further corresponding proportionalincreases in the output fluid pressures P P in the same manner aspreviously described, and since the input fluid pressures P,Paresubstantially equal, the forces P A P A acting across the switch pistons23,23a remain substantially equal obviating displacement of said switchpistons from their normally centered positions.

When the split system master cylinder is de-actuated, the input fluidpressures P i, are vented to the atmosphere which eliminates the forcesP,A ,P acting on the switch pistons 23,23a and sealing members 45,45aand the input forces P,(A -A ),P (A ,-A, acting on the proportioningpistons 33,33a. Upon the elimination of the input forces P (A A ),P (A Athe output fluid pressures P P acting on the sealing members 45,4511displace the lips 49,49a thereof from sealing engagement with thehousing counterbores 4,4a, andin this manner, the output fluid pressuresP return from the outlet ports 12,12a through the outlet chambers 53,53aand past the displaced sealing member lips 49,49a through the returnflow passages 50,50a into the inlet chambers 51,51a to the inlet ports11,11a. When the outlet fluid pressures P P are so reduced tocorrespondingly reduce the output forces F /l P 14, to a value less thanthe metering spring forces F,Fa, the metering springs 39,39a move theproportioning pistons 33,33a inwardly toward their original positionsre-engaging the stops 35,35a with the switch pistons 23,23a anddisplacing the valve members 44,44a from their seats 48,48a on thesealing members 45,45a to again open the sealing member apertures 46,46are-establishing open pressure fluid communication therethrough betweenthe inlet and outlet ports 11,11a and 12,12a to effect completeelimination of the output fluid pressures P P In the event of thefailure of the input fluid pressure P due to a malfunction of the splitsystem master cylnder or other leaks or the like, it is, of course,desirable to maintain the metering or proportioning function of theproportioning piston 33 under such emergency conditions; however, it isalso desirable to effect a change in the ratio between the input andoutput fluid pressures P P as discussed hereinafter. When the magnitudeof the input fluid pressure P exceeds that of the failed input fluidpressure P by a predetermined value, the force P A acting on the switchpiston 23 concertedly displaces the switch pistons 23,23a and theproportioning piston 33a against the force Fa of the metering spring 39arightwardly in the housing 2 toward a rightwardly displaced positionengaging the rightward end of the proportioning piston 33a with theclosure member 13, and of course, the compressive force Fa of themetering spring 39 concertedly urges the proportioning piston 33 towardthe rightwardly displaced position in following engagement with theswitch piston 23. The rightward movement of the proportioning piston 33to its rightwardly displaced position disengages the stepped extension36 from the closure member seal 20 and connects the change-over chamber52 in open pressure fluid communication with the inlet port 11, and inthis manner, the area 14 -14 on the proportioning piston 33 is subjectedto the input fluid pressure P,. When the input and output fluidpressures P ,P attain a predetermined value U on the line OT in thegraph of FIG. 3, the output fluid pressure P now acts on the effectivearea A of the proportioning piston 33 to establish the closing force itsisolating position to sealably engage the proportioning piston valvemember 44 with the sealing member valve seat 48 closing the sealingmember aperture 46 and isolating the input fluid pressure P at the inletport 11 from the outlet fluid pressure P at the output port 12. Ofcourse, since the effective area A is less than A,,, the predeterminedvalue U or knee-point of the curve OUV in the graph of FIG. 3 is greaterthan the predetermined value R, and since the compressive force F of themetering spring 39 is decreased upon the movement of the proportioningpiston 33 to its rightwardly displaced position, it is apparent that theslope of the line UV will be greater than that of the line ST in thegraph of FIG. 3. With the proportioning piston 33 in its isolatingposition, the closing force P A is replaced by the input force of theinput fluid pressure P acting on the input effectve area A -A which isadditive to the metering springforce F, and the input force P (A -A andadditive metering spring force F is substantially equal to and balancedby the output force of the output fluid pressure P acting on the outputeffective area A.

From the graphical representation in FIG. 3, it is obvious thatincreases in the magnitude of the input fluid pressure P, in excess ofthe predetermined value U, as shown on the line UT, will result inproportionally reduced increases in the output fluid pressure Po, asshown by the line UV. When the input fluid pressure P,

is increased to a value in excess of the predetermined value U, theinput force P (A -A is correspondingly increased and additive to themetering spring force F to overcome the output force P /1 therefore, themetering piston 33 is moved to its metering position disengaging thevalve member 44 thereof from the sealing member valve seat 48 to effectthe metered application of the input fluid pressure P through thesealing member aperture 46 and the outlet chamber 53 to the outlet port12 to effect the proportional increase in the output fluid pressure P inanother predetermined ratio with the input fluid pressure P at the inletport 11, as shown by the line UV in the graph of FIG. 3 wherein P =[P,(AA Fa]A Of course, the increased output fluid pressure P effects acorresponding increase in the output force P 14 and when the increasedoutput force P A attains a value substantially equal to the additiveinput force P,(A,-A and metering spring force F, the proportioningpiston 33 is again moved to its isolating position. The proportioningpiston 33 will be responsive to further increases in the input fluidpressure P, to effect further proportional increases in the output fluidpressure P in the same manner as previously described when the inputfluid pressure P is failed. Of course, when the split system mastercylinder is deactuated to vent the input fluid pressure P, toatmosphere, the input force P (A A is eliminated and the output fluidpressure P displaces the sealing member lip 49 from sealing engagementwith the housing counterbore 4 to open the sealing member return flowpassages 50 permitting the return flow therethrough of the output fluidpressure P to the inlet port 11, as previously mentioned. Upon thereduction of the output force P 14, to a value less than the meteringspring force F, the metering spring 39 moves the proportioning piston 33to its original position effecting open pressure fluid communicationbetween the inlet and outlet ports l1, 12 through the sealing memberaperture 46.

Of course, the concerted movement of the switch pistons 23, 23a to theirrightward displaced positions displaces the positioning land 27 thereoffrom beneath the follower member 62 of the switch 10 permitting theswitch spring 66 to urge said switch follower member downwardly intolocking engagement with the locking groove 28 of the switch piston 23thereby maintaining the switch pistons 23,23a and the proportioningpiston 33a in their rightward displaced or translated positions againstthe force Fa of the metering spring 39a. The downward movement of theswitch follower member 62 also moves the follower member contact 64 intocircuit making engagement with the switch contact 65 to energize thedriver warning or dash lamp (not shown).

When the fluid pressure integrity of the system has been re-established,removal of the switch 10 from the housing 2 disengages the switchfollower member 62 from locking engagement with the switch pistonpermitting the compressive force of the metering spring 39a toconcertedly move the switch pistons 23,23a and proportioning pistons33,33a from their rightwardly displaced positions toward their normalcentered positions against the force of the metering spring 39. Thismovement of the proportioning piston 33 leftwardly to its normalposition reengages the stepped extension 36 thereof with the closuremember seal thereby again interrupting pressure fluid communicationbetween the change-over chamber 52 and the inlet port 11. Any fluidpressure which might be trapped in the chamber 52 upon the engagement ofthe proportioning piston extension 36 with the closure member seal 20will bleed past said seal when the inlet fluid pressure P, is vented tothe atmosphere, as previously mentioned.

In the event of the failure of the input fluid pressure P,, the force P14 acting on the switch piston proportioning piston 33 toward theirleftward displaced or translated positions engaging the leftward end ofsaid proportioning piston with the closure member 13 and theproportioning piston 33a follows in response to the metering springforce Fa. The movement of the proportioning piston 33a to its leftwarddisplaced position permits actuation of the switch 10, as previouslydescribed, and disengages the stepped extension 36a from the closuremember seal 20a to connect the changeover chamber 521: in open pressurefluid communication with the inlet chamber 510 thereby subjecting theeffective area A -A to the inlet fluid pressure P at the inlet port 11a. In its leftward displaced position, the proportioning piston 33a isactuated in the same manner as that previously described for theproportioning piston 33 in its rightward displaced position; therefore,for the sake of brevity, the description of the operation of the piston33a in its leftward translated position is omitted.

From the foregoing, it is now apparent that a novel control valve 1 isdisclosed and that changes or modifications as to the preciseconfigurations, shapes and details of the construction set forth in thedisclosure by way of illustration may be made by those skilled in theart without departing from the spirit of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A control valve comprising a housing, means for comparing separatefluid pressures supplied to said housing and movable therein from anormally centered position toward opposed translated positions inresponse to oppositely acting differentials in excess of a predeterminedamount between the supplied fluid pressures acting thereon, a pair ofopposed proportioning means engaged for concerted movement in saidhousing with said comparing means between its centered and translatedpositions and movable relative to said comparing means in the centeredand translated positions thereof for performing proportioning operationson the separate .fluid pressures, said proportioning means beingoperable generally in response to the separate fluid pressures in excessof a predetermined value to effect separate proportionally reducedapplications thereof through said housing, respectively, an area on atleast one of said proportioning means isolated from fluid pressure insaid housing when said comparing means is in its centered position andsubjected to one of the separate fluid pressures upon the concertedmovement of said one proportioning means with said comparing means toone of its translated positions, and seal means normally engaged betweensaid housing and a portion of said one proportioning means to isolatesaid area from fluid pressure in said housing when said comparing meansand proportioning means are in the centered position, said seal meansbeing disengaged from one of said housing and said portion of said oneproportioning means to subject said area to the one separate fluidpressure upon the concerted movement of said one proportioning meanswith said comparing means to the one translated position, the magnitudeof the predetermined value at which the proportioning operation of saidone proportioning means occurs when said area is subjected to the oneseparate fluid pressure being predeterminately greater than anothermagnitude of the predetermined value at which the proportioningoperation of said one proportioning means occurs when said area isisolated from fluid pressure.

2. A control valve according to claim 1, comprising a pair of steppedextension means on said one proportioning means, one of said extensionmeans defining said portion of said one proportioning means, and ashoulder on said one proportioning means between said extension means,said area being on said shoulder, said seal means being engaged betweenone of said housing and said one extension means when said comparingmeans and proportioning means are in the centered position to isolatesaid area from the one separate fluid pressure and said seal means beingdisengaged from said one of said housing and said one extension meansupon the concerted movement of said comparing means and oneproportioning means to the one translated position to subject said areato the one separate fluid pressure.

3. A control valve according to claim 1, comprising other seal meansspacedfrom said first named seal means and sealably engaged between saidhousing and another portion of said one proportioning means, a chamberin said housing defined between said first named and other seal meansand isolated from the one separate fluid pressure in said housing whensaid first named and other seal means are engaged between said housingand said first named and other portions of said one proportioning means,respectively, said area being within said chamber when said comparingmeans and one proportioning means are in the centered position, and saidfirst named seal means being disengaged from said one of said housingand said first named portion of said one proportioning means to subjectsaid chamber and area to the one separate fluid pressure upon theconcerted movement of said comparing means and one proportioning meansto the one translated position.

4. A control valve according to claim 3, comprising a pair of steppedextensions on said one proportioning means respectively defining saidfirst named and other portions thereof, said first named and other sealmeans being respectively engaged between said housing and said extensionmeans when said comparing means and one proportioning means are in thecentered position, a shoulder on said one proportioning means betweensaid extension means defining said area, said shoulder being within saidchamber when said comparing and one proportioning means are in thecentered position, and said first named seal means being disengaged fromone of said housing and one of said extension means to subject'saidchamber and area to the one separate fluid pressure upon the concertedmovement of said comparing means and one proportioning means to the onetranslated position.

5. A control valve according to claim 1, wherein said one proportioningmeans includes resiliently urged means, said resiliently urged meansbeing initially respectively movable in the centered and one translatedpositions thereof against its own force in response to the one separatefluid pressure of the other and first named magnitudes acting thereontoward an isolating position in said housing interrupting the flow ofthe one fluid pressure therethrough and being thereafter further movablein response to its own force assisted by increases in the one separatefluid pressure in excess of the other and first named magnitudes actingthereon toward a metering position to perform its proportioningoperation and effect the separate proportionally reduced apllication ofthe one separate fluid pressure through said housing; said resilientlyurged means also being urged by its own force toward engagement withsaid comparing means for the concerted movement thereof between thecentered and one translated positions, and said area and said portion ofsaid one proportioning means being on said resiliently urged means.

6. A control valve according to claim 5, wherein said resiliently urgedmeans includes a proportioning piston movable in said housing, andspring means engaged with said proportioning piston, said area and saidportion of said one proportioning means being on said proportioningpiston, said proportioning piston being respectively initially movablein each of the centered and translated positions against the force ofsaid spring means in response to the one separate fluid pressure of theother and first named magnitudes acting on said proportioning pistontowards the isolating position in said housing interrupting the flow ofthe one fluid pressure therethrough and being thereafter further movablein response to the force of said spring means assisted by increases inthe one separate fluid pressure in excess of the other and first namedmagnitudes acting on said proportioning piston toward the meteringposition to perform its proportioning operation and establish theproportionally reduced applied fluid pressure, and the force of saidspring means assisting the concerted movement of said comparing meansand one proportioning piston toward the one translated position.

7. A control valve according to claim 6, comprising extension means onsaid proportioning piston and engaged with said seal means to isolatesaid area when said comparing means and proportioning piston are in thecentered position, said seal means being disengaged from one of saidhousing and extension means to subject said area to the one fluidpressure upon the concerted movement of said comparing means andproportioning piston to the one translated position.

8. A control valve according to claim 6, comprising a pair of steppedextensions on said proportioning piston, one of said extensions definingsaid portion of said one proportioning means, other seal means spacedfrom said first named seal means and sealably engaged between saidhousing and the other of said extensions, a chamber in said housingdefined between said first named and other seal means and isolated fromthe one separate fluid pressure when said first named and other sealmeans are engaged between said housing and said extensions,respectively, a shoulder on said proportioning piston between saidextensions defining said area and being within said chamber when saidproportioning piston is in the centered position, and said first namedseal means being disengaged from one of said housing and said oneextension to subject said chamber and area to the one separate fluidpressure upon the concerted movement of said comparing means andproportioning piston to the one translated position.

9. A control valve according to claim 6, comprising opposed input andoutput areas on said proportioning piston subjected to the one separatefluid pressure, said proportioning piston being respectively initiallymovable in each of the centered and translated positions against theforce of said spring means in response to the one separate fluidpressure of the other and first named magnitudes acting on said opposedinput and output areas towards the isolating position and beingthereafter further movable in response to the force of said spring meansassisted by increases in the one separate fluid pressure in excess ofthe other and first named magnitudes acting on said input area to themetering position to perform its proportioning operation and establishthe proportionally reduced applied fluid pressure acting on the outputarea, said first named area being additive to said input area andsubject to the one separate fluid pressure when said comparing means andproportioning piston are in the one translated position.

10. A control valve according to claim 9, wherein said output area ispredeterminately greater than said input area.

11. A control valve according to claim 9, wherein said output area ispredeterminately greater than the additive input area and said firstnamed area.

12. A control valve comprising a housing, concertedly and relativelymovable comparator means and a pair of opposed proportioning means insaid housing and defining therewith a pair of opposed sets of inlet andoutlet chambers, said comparator means and proportioning means beingconcertedly movable between a normally centered position and opposedtranslated positions in said housing upon preselected conditions and atleast one of said proportioning means being movable relative to saidcomparator means in each of said positions for performing proportioningoperations on the fluid pressures between the inlet and outlet chambersof at least one of said chamber sets, said one proportioning means beingmovable relative to said comparator means in the centered position andone of the translated positions in response to fluid pressure in excessof first and second predetermined values in the inlet chamber of saidone chamber set to establish a proportionally reduced fluid pressure inthe outlet chamber of said one chamber set in first and secondpredetermined ratios with the fluid pressure in the inlet chamber ofsaid one chamber set in excess of the first and second predeterminedvalues, respectively, an area on said one proportioning means forisolation from and subjection to the fluid pressure in the inlet chamberof said one chamber set when said comparator and proportioning means arein the centered and one translated positions, respectively, and asealing member normally engaged between said housing and a portion ofsaid one proportioning means to isolate said area from the fluidpressure in the inlet chamber of said one chamber set when saidcomparator means and one proportioning means are in the centeredposition, said sealing member being disengaged from one of said housingand said portion of said proportioning means to subject said area to thefluid pressure in the inlet chamber of said one chamber set upon theconcerted movement of said one proportioning means with said comparatormeans to the one translated position, the magnitude of the secondpredetermined value at which the proportioning operation of said oneproportioning means occurs when said third area is subjected to thefluid pressure in the inlet chamber of said one chamber set beingpredeterminately greater than that of the first predetermined value atwhich the proportioning operation of said one proportioning means occurswhen said area is isolated from fluid pressure.

13. A control valve comprising a housing, concertedly and relativelymovable comparator means and a pair of proportioning means in saidhousing and defining with said housing a pair of pressure fluid flowpassages therethrough for separate supplied fluid pressures, saidcomparator and proportioning means being concertedly movable in saidhousing between a normally centered position and opposed translatedpositions and at least one of said proportioning means being movablerelative to said comparator means in each of said positions to performproportioning operations on the supplied fluid pressure in at least oneof said flow passages, respectively, said one proportioning means beingmovable relative to said comparator means in re-' sponse to the suppliedfluid pressure in said one flow passage in excess of a predeterminedvalue acting thereon to effect a proportionally reduced applicationthereof through said one flow passage, a pair of opposed areas on saidcomparator means respectively subjected to the supplied fluid pressuresin said flow passages, said comparator means and proportioning meansbeing concertedly movable toward one of the opposed translated positionin response to the supplied fluid pressure in said one flow passageacting on one of said opposed areas upon the failure of the suppliedfluid pressure in the other of said flow passages acting on the other ofsaid areas, a seal engaged between said housing and a portion of saidone proportioning means defining therewith a chamber for selectiveisolation from and subjection to thesupplied fluid pressure in said oneflow passage, said seal being disengaged from one of said housing andsaid portion of said one proportioning means to subject said chamber tothe supplied fluid pressure in said one flow passage upon the concertedmovement of said comparator means and proportioning means to the onetranslated position, a third area in said chamber on said oneproportioning means isolated from the supplied fluid pressure in saidone flow passage when said seal is engaged with said one of said housingand portion of said one proportioning means and subjected to thesupplied fluid pressure in said one flow passage upon the disengagementof said seal from said one of said housing and portion of said oneproportioning means, respectively, the predetermined value at which theproportioning operation of said one proportioning means occurs when saidthird area and chamber are subjected to the supplied fluid pressure insaid one passage being greater than the predetermined value at which theproportioning operation of said one proportioning means occurs when saidthird area and chamber are isolated.

14. A control valve comprising a housing having a pair of sets of inletand outlet ports therein, means for comparing the magnitudes of thefluid pressures at the inlet ports of said port sets and movable in saidhousing between said port sets from a normally centered position towardopposed translated positions in response to oppositely actingdifferentials in excess of a predetermined amount between the magnitudesof the fluid pressures at the inlet ports of said port sets actingthereon, a pair of proportioning means engaged for concerted movementwith said comparing means between the centered and translated positionsand movable relative to said comparing means in the centered positionand the translated positions for performing proportioning operations onthe fluid pressures between the inlet and outlet ports of said portsets, at least one of said proportioning means being operable generallyin response to the fluid pressures at the inlet port of one of said portsets in excess of a predetermined value to establish a proportionallyreduced fluid pressure at the outlet port of said one port set in thecentered and one of the translated positions, respectively,

an area on said one proportioning means isolated from and subjected tothe fluid pressure at the inlet port of said one port set when saidcomparing means and proportioning means are in the centered position andthe one translated position, respectively, a seal engaged between saidhousing and a portion of said one proportioning means to isolate saidarea from the fluid pressure at the inlet port of said one port set whensaid comparator means and proportioning means are in the centeredposition, said seal means being disengaged from one of said housing andsaid portion of said one proportioning means to subject said area to thefluid pressure at the inlet port of said one port set upon the concertedmovement of said comparator means and proportioning means to the onetranslated position, and the predetermined value at which theproportioning operation of said one proportioning means occurs when saidarea is subjected to the fluid pressure at the inlet port of said oneport set being predeterminately in excess of that at which theproportioning operation of said one proportioning means occurs when saidarea is isolated from the fluid pressure at the inlet port of said oneport set.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,738,709 Issued June 12, 1973 Stanley L. Stokes It is certified thaterrors appear in the abovetginosigfied Letters Patent which is herebycorrect as shown Column 1 line 3, delete "3,27,385" and insert 3,627,385Column 2,

line 20, after "16a" insert a comma line 64, after "extending" insertside walls 43, 43s and 44, 44a, said side vi e 11s 44, 44a Column 3,line 32,

after "cross-sectional" insert areas A A defined by the sealingengagement of the Column 4, line 29, "l should read P line 31,"substantislll" should read substantially line 35, after "33, 33s"insert to establish closing forces P A P A urging said line 62, after "Ainsert a comma Column 5, line 8, after "P insert a coma line 25, after"of" insert FIG. 3 wherein line 29, "P A should read-P A line #3, "P P"should read P P line 50, "P A P should read P A P A line 55, "P L shouldread P P Column 6, line 40, after "force" insert P A urging saidproportioning piston leftwerdly toward line 45, "output" should readoutlet columi' if 11m 14, "[P (A A sals should read Column 8, line 6,after "piston" insert 23s concerte ly moves the switch pistons 23, 23aand the Column 10, line hz, after "one" insert separate I Signed andsealed this 26th day of February 1974 (SEAL) Attest:

EDWARD -M.FLETCHER,JR. C. MARSHALL DANN Attestlng Officer Commissionerof Patents

1. A control valve comprising a housing, means for comparing separatefluid pressures supplied to said housing and movable therein from anormally centered position toward opposed translated positions inresponse to oppOsitely acting differentials in excess of a predeterminedamount between the supplied fluid pressures acting thereon, a pair ofopposed proportioning means engaged for concerted movement in saidhousing with said comparing means between its centered and translatedpositions and movable relative to said comparing means in the centeredand translated positions thereof for performing proportioning operationson the separate fluid pressures, said proportioning means being operablegenerally in response to the separate fluid pressures in excess of apredetermined value to effect separate proportionally reducedapplications thereof through said housing, respectively, an area on atleast one of said proportioning means isolated from fluid pressure insaid housing when said comparing means is in its centered position andsubjected to one of the separate fluid pressures upon the concertedmovement of said one proportioning means with said comparing means toone of its translated positions, and seal means normally engaged betweensaid housing and a portion of said one proportioning means to isolatesaid area from fluid pressure in said housing when said comparing meansand proportioning means are in the centered position, said seal meansbeing disengaged from one of said housing and said portion of said oneproportioning means to subject said area to the one separate fluidpressure upon the concerted movement of said one proportioning meanswith said comparing means to the one translated position, the magnitudeof the predetermined value at which the proportioning operation of saidone proportioning means occurs when said area is subjected to the oneseparate fluid pressure being predeterminately greater than anothermagnitude of the predetermined value at which the proportioningoperation of said one proportioning means occurs when said area isisolated from fluid pressure.
 2. A control valve according to claim 1,comprising a pair of stepped extension means on said one proportioningmeans, one of said extension means defining said portion of said oneproportioning means, and a shoulder on said one proportioning meansbetween said extension means, said area being on said shoulder, saidseal means being engaged between one of said housing and said oneextension means when said comparing means and proportioning means are inthe centered position to isolate said area from the one separate fluidpressure and said seal means being disengaged from said one of saidhousing and said one extension means upon the concerted movement of saidcomparing means and one proportioning means to the one translatedposition to subject said area to the one separate fluid pressure.
 3. Acontrol valve according to claim 1, comprising other seal means spacedfrom said first named seal means and sealably engaged between saidhousing and another portion of said one proportioning means, a chamberin said housing defined between said first named and other seal meansand isolated from the one separate fluid pressure in said housing whensaid first named and other seal means are engaged between said housingand said first named and other portions of said one proportioning means,respectively, said area being within said chamber when said comparingmeans and one proportioning means are in the centered position, and saidfirst named seal means being disengaged from said one of said housingand said first named portion of said one proportioning means to subjectsaid chamber and area to the one separate fluid pressure upon theconcerted movement of said comparing means and one proportioning meansto the one translated position.
 4. A control valve according to claim 3,comprising a pair of stepped extensions on said one proportioning meansrespectively defining said first named and other portions thereof, saidfirst named and other seal means being respectively engaged between saidhousing and said extension means when said comparing means and oneproportioning means are in the centered position, a shoulder on said oneproportioning means between said extension means defining said area,said shoulder being within said chamber when said comparing and oneproportioning means are in the centered position, and said first namedseal means being disengaged from one of said housing and one of saidextension means to subject said chamber and area to the one separatefluid pressure upon the concerted movement of said comparing means andone proportioning means to the one translated position.
 5. A controlvalve according to claim 1, wherein said one proportioning meansincludes resiliently urged means, said resiliently urged means beinginitially respectively movable in the centered and one translatedpositions thereof against its own force in response to the one separatefluid pressure of the other and first named magnitudes acting thereontoward an isolating position in said housing interrupting the flow ofthe one fluid pressure therethrough and being thereafter further movablein response to its own force assisted by increases in the one separatefluid pressure in excess of the other and first named magnitudes actingthereon toward a metering position to perform its proportioningoperation and effect the separate proportionally reduced apllication ofthe one separate fluid pressure through said housing, said resilientlyurged means also being urged by its own force toward engagement withsaid comparing means for the concerted movement thereof between thecentered and one translated positions, and said area and said portion ofsaid one proportioning means being on said resiliently urged means.
 6. Acontrol valve according to claim 5, wherein said resiliently urged meansincludes a proportioning piston movable in said housing, and springmeans engaged with said proportioning piston, said area and said portionof said one proportioning means being on said proportioning piston, saidproportioning piston being respectively initially movable in each of thecentered and translated positions against the force of said spring meansin response to the one separate fluid pressure of the other and firstnamed magnitudes acting on said proportioning piston towards theisolating position in said housing interrupting the flow of the onefluid pressure therethrough and being thereafter further movable inresponse to the force of said spring means assisted by increases in theone separate fluid pressure in excess of the other and first namedmagnitudes acting on said proportioning piston toward the meteringposition to perform its proportioning operation and establish theproportionally reduced applied fluid pressure, and the force of saidspring means assisting the concerted movement of said comparing meansand one proportioning piston toward the one translated position.
 7. Acontrol valve according to claim 6, comprising extension means on saidproportioning piston and engaged with said seal means to isolate saidarea when said comparing means and proportioning piston are in thecentered position, said seal means being disengaged from one of saidhousing and extension means to subject said area to the one fluidpressure upon the concerted movement of said comparing means andproportioning piston to the one translated position.
 8. A control valveaccording to claim 6, comprising a pair of stepped extensions on saidproportioning piston, one of said extensions defining said portion ofsaid one proportioning means, other seal means spaced from said firstnamed seal means and sealably engaged between said housing and the otherof said extensions, a chamber in said housing defined between said firstnamed and other seal means and isolated from the one separate fluidpressure when said first named and other seal means are engaged betweensaid housing and said extensions, respectively, a shoulder on saidproportioning piston between said extensions defining said area andbeing within said chamber when said proportioning piston is in thecentered position, and said first named seal means being disEngaged fromone of said housing and said one extension to subject said chamber andarea to the one separate fluid pressure upon the concerted movement ofsaid comparing means and proportioning piston to the one translatedposition.
 9. A control valve according to claim 6, comprising opposedinput and output areas on said proportioning piston subjected to the oneseparate fluid pressure, said proportioning piston being respectivelyinitially movable in each of the centered and translated positionsagainst the force of said spring means in response to the one separatefluid pressure of the other and first named magnitudes acting on saidopposed input and output areas towards the isolating position and beingthereafter further movable in response to the force of said spring meansassisted by increases in the one separate fluid pressure in excess ofthe other and first named magnitudes acting on said input area to themetering position to perform its proportioning operation and establishthe proportionally reduced applied fluid pressure acting on the outputarea, said first named area being additive to said input area andsubject to the one separate fluid pressure when said comparing means andproportioning piston are in the one translated position.
 10. A controlvalve according to claim 9, wherein said output area is predeterminatelygreater than said input area.
 11. A control valve according to claim 9,wherein said output area is predeterminately greater than the additiveinput area and said first named area.
 12. A control valve comprising ahousing, concertedly and relatively movable comparator means and a pairof opposed proportioning means in said housing and defining therewith apair of opposed sets of inlet and outlet chambers, said comparator meansand proportioning means being concertedly movable between a normallycentered position and opposed translated positions in said housing uponpreselected conditions and at least one of said proportioning meansbeing movable relative to said comparator means in each of saidpositions for performing proportioning operations on the fluid pressuresbetween the inlet and outlet chambers of at least one of said chambersets, said one proportioning means being movable relative to saidcomparator means in the centered position and one of the translatedpositions in response to fluid pressure in excess of first and secondpredetermined values in the inlet chamber of said one chamber set toestablish a proportionally reduced fluid pressure in the outlet chamberof said one chamber set in first and second predetermined ratios withthe fluid pressure in the inlet chamber of said one chamber set inexcess of the first and second predetermined values, respectively, anarea on said one proportioning means for isolation from and subjectionto the fluid pressure in the inlet chamber of said one chamber set whensaid comparator and proportioning means are in the centered and onetranslated positions, respectively, and a sealing member normallyengaged between said housing and a portion of said one proportioningmeans to isolate said area from the fluid pressure in the inlet chamberof said one chamber set when said comparator means and one proportioningmeans are in the centered position, said sealing member being disengagedfrom one of said housing and said portion of said proportioning means tosubject said area to the fluid pressure in the inlet chamber of said onechamber set upon the concerted movement of said one proportioning meanswith said comparator means to the one translated position, the magnitudeof the second predetermined value at which the proportioning operationof said one proportioning means occurs when said third area is subjectedto the fluid pressure in the inlet chamber of said one chamber set beingpredeterminately greater than that of the first predetermined value atwhich the proportioning operation of said one proportioning means occurswhen said area is isolated from fluid pressure.
 13. A contRol valvecomprising a housing, concertedly and relatively movable comparatormeans and a pair of proportioning means in said housing and definingwith said housing a pair of pressure fluid flow passages therethroughfor separate supplied fluid pressures, said comparator and proportioningmeans being concertedly movable in said housing between a normallycentered position and opposed translated positions and at least one ofsaid proportioning means being movable relative to said comparator meansin each of said positions to perform proportioning operations on thesupplied fluid pressure in at least one of said flow passages,respectively, said one proportioning means being movable relative tosaid comparator means in response to the supplied fluid pressure in saidone flow passage in excess of a predetermined value acting thereon toeffect a proportionally reduced application thereof through said oneflow passage, a pair of opposed areas on said comparator meansrespectively subjected to the supplied fluid pressures in said flowpassages, said comparator means and proportioning means beingconcertedly movable toward one of the opposed translated position inresponse to the supplied fluid pressure in said one flow passage actingon one of said opposed areas upon the failure of the supplied fluidpressure in the other of said flow passages acting on the other of saidareas, a seal engaged between said housing and a portion of said oneproportioning means defining therewith a chamber for selective isolationfrom and subjection to the supplied fluid pressure in said one flowpassage, said seal being disengaged from one of said housing and saidportion of said one proportioning means to subject said chamber to thesupplied fluid pressure in said one flow passage upon the concertedmovement of said comparator means and proportioning means to the onetranslated position, a third area in said chamber on said oneproportioning means isolated from the supplied fluid pressure in saidone flow passage when said seal is engaged with said one of said housingand portion of said one proportioning means and subjected to thesupplied fluid pressure in said one flow passage upon the disengagementof said seal from said one of said housing and portion of said oneproportioning means, respectively, the predetermined value at which theproportioning operation of said one proportioning means occurs when saidthird area and chamber are subjected to the supplied fluid pressure insaid one passage being greater than the predetermined value at which theproportioning operation of said one proportioning means occurs when saidthird area and chamber are isolated.
 14. A control valve comprising ahousing having a pair of sets of inlet and outlet ports therein, meansfor comparing the magnitudes of the fluid pressures at the inlet portsof said port sets and movable in said housing between said port setsfrom a normally centered position toward opposed translated positions inresponse to oppositely acting differentials in excess of a predeterminedamount between the magnitudes of the fluid pressures at the inlet portsof said port sets acting thereon, a pair of proportioning means engagedfor concerted movement with said comparing means between the centeredand translated positions and movable relative to said comparing means inthe centered position and the translated positions for performingproportioning operations on the fluid pressures between the inlet andoutlet ports of said port sets, at least one of said proportioning meansbeing operable generally in response to the fluid pressures at the inletport of one of said port sets in excess of a predetermined value toestablish a proportionally reduced fluid pressure at the outlet port ofsaid one port set in the centered and one of the translated positions,respectively, an area on said one proportioning means isolated from andsubjected to the fluid pressure at the inlet port of said one port setwhen said comparing means and proportioning means are in the centeredposition and the one translated position, respectively, a seal engagedbetween said housing and a portion of said one proportioning means toisolate said area from the fluid pressure at the inlet port of said oneport set when said comparator means and proportioning means are in thecentered position, said seal means being disengaged from one of saidhousing and said portion of said one proportioning means to subject saidarea to the fluid pressure at the inlet port of said one port set uponthe concerted movement of said comparator means and proportioning meansto the one translated position, and the predetermined value at which theproportioning operation of said one proportioning means occurs when saidarea is subjected to the fluid pressure at the inlet port of said oneport set being predeterminately in excess of that at which theproportioning operation of said one proportioning means occurs when saidarea is isolated from the fluid pressure at the inlet port of said oneport set.